Our research aims at understanding the regulation of eukaryotic gene expression, particularly the role played by chromatin architecture in transcription. Principle objectives in general are to examine the chemical composition (protein, RNA and DNA content) and ultimately the physical structure of active genes and to characterize the proteins in active gene regions associated with DNA or RNA. Current emphasis lies in studying the portein chemistry and in situ location of non-hisone nuclear proteins. Drosophila melanogaster is used for this research because of its many synergistic advantages included well-defined genetics, small genome size and the existence of techniques for localizing RNA and protein molecules and specific gene sequences in polytene chromosomes. Recombinant DNA technology is being vigorously applied to Drosophila, leading to a rapid explosion in our knowledge of Drosophila gene organization. A growing number of cloned genes chromosomal segments are available for probing details of chromatin architecture and gene expression. We are characterizing HMG-like polypeptides from Drosophila, attempting to relate the Drosophila polypeptides to mammalian and trout HMGs which are already well characterized. We are also attempting to ascertain the chromosomal location of these polypeptides by using immunofluorescent techniques. We are also characterizing Drosophila nuclear ribonucleoprotein particles, and comparing the polypeptides associated with RNA with bulk non-histone chromosomal proteins. We will carry out immunofluorescent analysis of the chromosomal location of the major polypeptides associated with nascent, nuclear RNA molecules. As a first step toward enriching for active chromatin, we are examining the proteins and chromosomal structures released from intact nuclei by micrococcal nuclease and by DNase I under a variety of experimental conditions.